1. Field of the Invention
The invention relates to a control device for differential speed steering of a vehicle with an arrangement of four control valves assigned in pairs to respectively two directions of two degrees of freedom, their outputs being connected to control connectors regulating the forward and reverse movements of a right and left driving element by means of respective steering and drive control positions of the spool valve via reversing valves, which cause a steering reversal in the forward-reverse movement sense.
2. The Prior Art
A differential speed steering device is known from German Patent DE-PS No. 25 11 176, in which four controllable valves are arranged around the circumference of a control lever, each one of the two which are arranged opposite to each other serves as forward and reverse control and the other two, being disposed laterally, are used for a differential drive control of a right and left hydraulically operated drive by means of interposed shuttle valves. Operation of the device by means of the steering lever movable in two dimensions considerably differs from the customary steering and speed control by means of two operating elements, which are separately movable in a single dimension, of other types of vehicles. There is the additional disadvantage that in order to move in a tight turn, the reverse movement of the one drive and the simultaneous forward movement of the other drive is only possible by the additional operation of a special reversing valve, which further complicates operation and differs from the usual operation and also results in discontinuous steering and driving operations.
The many diverse steering elements and their connections to each other are complicated and pose increased safety risks. Additionally, straight movement requires constant steering and exact matching of the pressure conditions in the control and reversing valves.